1. Field of the Invention
The present invention relates to a brake device mounted on the gymnastic equipment to control the motion loading of, and more particularly to a two-in-one magnetic control device which makes use of the externally rotary fly wheel to generate power and to control the loading condition.
2. Description of the Prior Art
The brake (loading) device for conventional indoor exercise equipment makes use of no other than friction type, oil pressure type, fan type, etc. The friction type brake device has inconvenience of oil leakage, noise-making and reduction of braking effect at a high temperature while the fan type has drawbacks with huge volume, poor appearance, narrow loading range and difficult adjustment.
Accordingly, the eddy current type resistance formed by the change of the magnetic field is made used recently. Since it belongs a non-contact form of magnetic control, it was highly appreciated on the market. Such device was disclosed in the application (No. 79206996) in Taiwan R.O.C. which is called "permanent magnet type adjustable brake device" (U.S. Pat. No. 5,096,024); one amendment thereto was applied as No. 79206996 and U.S. Pat. No. 5,437,353. In addition, it was also disclosed in the R.O.C. Patent No. 80211672 "Eddy combined magnetic field resistance brake device" (U.S. Pat. No. 5,234,083), R.O.C. Patent No. 82218230 "Magnetic loading system of magnetic control for gymnastic car", R.O.C. Patent No. 82215087 "Loading adjustment device with magnetic control for gymnastic car", R.O.C. Patent No. 85207333 "Magnetic control braking device with lateral movement type for gymnastic car", R.O.C. Patent No. 86213735 "Magnetic control wheel for gymnastic car", and the following U.S. Pat. Nos.:
1. 5,072,930; PA0 2. 5,236,069; PA0 3. 5,586,624; and PA0 4. 4,775,145.
In the above-mentioned applications of magnetic control device with eddy current type, their basic principle is that conductor is placed in the variable magnetic flux so that a reverse electromotive force is generated on the locally closed circuit inside of the conductor so that the so-called eddy current is produced. The flow direction of this eddy current building the magnetic effect must be contrary to the variable direction of the original magnetic flux creating this current. Moreover, the Max-well's Equation tells that this magnetic force is proportional to the square of the density of the magnetic flux. It is just required by the brake (loading) of the gymnastic equipment.
Although the magnetic control device with eddy current type has its advantages and features, it is difficult for the loading part, when the permanent magnet is used to be the magnetic field source, to be connected to the external digital signal to reach the goal of computerization and digitalization, unless a motor and a motor controller are extra installed to change the relative position of the magnet and the conductor, or electromagnetic coil and extra added power are used to overcome this difficulty which bring much inconvenience in usage and the practicalness is therefore reduced, so that it can only be applied to the gymnastic equipment with lower price. Nevertheless, the accuracy and the real effect are taken more and more seriously to the gymnastic equipment, and it can only be reached by means of the computerization and digitalization. In addition, the gymnastic equipment with digitalized functions should be equipped with gauges and controllers which also require power. When the power is supplied from outside, it brings a lot of troubles and restrictions.
Accordingly, the inventor has developed a permanent magnetic three-phase AC brake device by the way of generator to be the loading for the gymnastic and rehabilitative equipment. A conventional permanent magnetic three-phase AC generator makes use of the magnetic field created by the current value on the stator coil which is a "reverse filed" resulting in a reverse torque to form a "loading", so that the current value of the stator coil must be very great, otherwise an appropriate resistance is not able to be produced. Thus, it results in disadvantages of a huge volume and an expensive production price. Furthermore, the permanent magnetic AC generator has resonance point, so that the loading control is very unstable. Consequently, it is not a completely practical brake device.
Besides, the outer edge of a circular copper strip is coaxially cut into a central gap an electromagnet to form the braking resistance. However, the copper strip is thin and large, and the flatness processing and installation are very difficult, so that the gap between the copper strip and the electromagnet is not able to be fix when the copper strip rotates. Therefore, the loading is very unstable, the whole structure is complex and it is not proper to be installed in the gymnastic equipment.